Packages for carrying sterile articles such as dressings, surgical devices, or the like, are frequently rendered sterile by subjecting the package and its contents to autoclaving temperatures of the order of at least 250.degree. F. It is desirable that such packages be peelable to deliver the contents thereof in a sterile field. Since such packages are normally formed from a web or webs with a coating of peelable heat sealing composition between panel portions of such webs; it has been found that a subsequent autoclaving operation tends to impair or nullify the peel characteristic of the heat sealing composition.
It has been proposed to overcome the undesirable increase in bonding of peelable packaging due to the autoclaving temperatures, by either (1) reducing the initial sealing temperatures, or (2) decreasing pressure of the sealing operation, or (3) shortening the dwell time at the point of seal.
However such expedients, in effect, produce undersealed packages which tend to exhibit leakage in the original seal and impair the maintenance of sterility in the final autoclaved package.
If the usual sealing temperatures, pressures and dwell periods are used; the subsequent autoclaving temperatures can increase the bond of the heat seals, which impairs the peelable characteristic of the autoclaved package.
Accordingly, an object of this invention is to provide a package of the type which must be subject to autoclaving to render the contents thereof sterile; where the peripheral portions of the panels forming the package are secured together by a heat sealing composition which on the one hand forms a uniform tight, non-leaking seal; and on the other hand, such seal is still subject to easy peeling when opening the autoclaved package to gain access to the sterile contents thereof.
Another object of this invention is to provide a package of the character set forth, wherein the sealing composition is constituted primarily of a thermoplastic resin having good seal and peel properties, and a modifier of a plastic character the sealing composition retaining its normal seal and peel properties despite exposure of the sealed packaging to elevated autclaving temperatures.
Still another object of this invention is to provide packaging of the character described, wherein the heat sealing composition is made up of selected vinyl polymers and a modifier of nitrocellulose; such composition being stable in respect of its sealing and peeling properties despite being subjected to elevated autoclaving temperatures.
Other objects of this invention will in part be obvious and in part hereinafter pointed out.